Rupturing Capacities of Oil Circuit Breakers

Abstract

This paper is really a series of more or less disconnected notes dealing with the question of rupturing capacity. of oil breakers. It makes no attempt to go into the theory of circuit-breaker design, and its main object is to open up a discussion regarding the advisability of using the term ``Maximum Safe Rupturing Capacity'' to describe the result obtained by the root-mean-square of the maximum peak of the current wave that occurs while the breaker is opening, multiplied by the root-mean-square of the open-circuit voltage that occurs immediately after the breaker opens. Attention is called to the different ratings due to use of peak values and root-mean-square values of current and voltage. It is recommended that an oil switch or an oil circuit breaker should be given a rating on the basis of maximum safe rupturing capacity that it can handle, and that a breaker after opening a short circuit up to its rating, should be immediately reclosable, and able to again open up a similar short circuit; breaker should open three successive short circuits before contacts need be repaired or oil replaced; these short circuits may be as close as two minutes apart.